In order to improve current quality of the 5-level cascaded H-bridge static synchronous compensator (STATCOM) based on carrier phase disposition pulse width modulation (PD-PWM), a control strategy aiming to balance the DC voltage is proposed. The STATCOM control system and the method of pulse cycle rotation based on PD-PWM are described. The influence that the pulse rotation time sequence exerts on DC side voltage of each H-bridge module is analyzed. Relation between duty ratio of the pulse rotation time sequence and positive power absorbed by the H-bridge module is deduced. Based on this, an improved pulse rotation control strategy which can adjust the duty ratio of pulse rotation time sequence to balance the DC side voltage of each H-bridge module is put forward. The simulations of the pulse cycle rotation and the improved strategy are analyzed based on STATCOM system. The simulation results verify the validity of the improved strategy.